Control apparatus, control method, and ophthalmologic apparatus including the control apparatus

ABSTRACT

In an ophthalmologic apparatus in which a head part is moved at a speed according to a rotation speed of a rotational part of a joystick, in order to enable a moving amount of the head part to correspond to a rotation amount even when the rotation speed becomes higher, the rotation speed of the joystick is detected at predetermined intervals, and when a current rotation speed (count of an encoder during a predetermined period) is lower than a previous rotation speed, a speed obtained by subtracting a predetermined value from the previous rotation speed is compared to the current rotation speed. Then, a higher speed is set as the current rotation speed, and the head part is moved at the speed corresponding to the current rotation speed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a control apparatus including ajoystick for controlling a control target, a control method, and anophthalmologic apparatus including the control apparatus to electricallyperform vertical movement of an optical system as the control target,for imaging and measurement of an eye to be inspected.

2. Description of the Related Art

As a configuration for controlling a control target with a joystick, afundus camera including a joystick to control an optical system may betaken as an example. In a conventional ophthalmologic apparatus such asthe fundus camera, the joystick is used for positional alignment betweenthe optical system of the apparatus and an eye to be inspected. In suchan apparatus, the joystick is inclined to perform back-and-forthmovement and lateral movement, while the joystick is rotated to performvertical movement. More specifically, there are known an apparatus inwhich the optical system is vertically moved manually by rotating a feedscrew of a vertical movement drive mechanism of the optical system incombination with a belt, a gear, and the like, and an apparatus in whichthe optical system is vertically moved electrically. As the apparatus inwhich the optical system is vertically moved electrically, there isknown an apparatus in which a motor is controlled so that the opticalsystem is moved at a speed proportional to a rotation speed of thejoystick (see Japanese Patent Application Laid-Open No. H05-317250).Further, there is known an apparatus in which the motor is controlled sothat the optical system is moved at a speed nonlinear with respect tothe rotation speed of the joystick, and as the joystick is rotated morequickly, the optical system can be moved at higher speed (see JapanesePatent No. 3,237,907).

However, in each of the apparatuses described in Japanese PatentApplication Laid-Open No. H05-317250 and Japanese Patent No. 3,237,907,the rotation speed of the motor has an upper limit, and hence, when therotation speed of the joystick becomes a fixed value or larger, themoving speed reaches to the upper limit though the joystick is rotatedeven quickly. Therefore, there arises a problem that the moving amountconversely decreases when the joystick is rotated quickly. There is amethod in which a motor having a higher upper limit of the rotationspeed is employed to control the motor to track the rotation speed ofthe joystick, but in this case, the high-performance motor is generallylarge in size and expensive. Further, a high-output power source isnecessary to drive the motor, resulting in a problem that the apparatusbecomes expensive and large in size.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus, including: a joystick forcontrolling a control target; a detection unit for repeatedly detectinga rotation amount of a rotational member provided to the joystick; and acontrol unit for outputting a control value corresponding to therotation amount according to the detection, in which when a decrease inthe rotation amount, in which an amount of decrease in the control valueper unit time exceeds a threshold value, has occurred, the control unitrestricts the amount of decrease in the control value per unit time to avalue that avoids exceeding the threshold value.

Further, the present invention relates to a control method for anapparatus including a joystick for controlling a control target, thecontrol method including: repeatedly detecting a rotation amount of arotational member provided to the joystick; outputting a control valuecorresponding to the rotation amount according to the detecting;determining whether or not a decrease in the rotation amount, in whichan amount of decrease in the control value per unit time exceeds athreshold value, has occurred; outputting, when it is determined thatthe decrease in the rotation amount does not occur, the control value sothat a sum of the control values to be output becomes a first valuecorresponding to a sum of the detected rotation amounts; andrestricting, when it is determined that the decrease in the rotationamount has occurred, the amount of decrease in the control value perunit time to a value that avoids exceeding the threshold value to outputthe control value so that the sum of the control values becomes largerthan the first value.

In addition, the present invention relates to an ophthalmologicapparatus including: detection means for detecting a rotation speed anda rotation direction of a rotational member provided to a joystick atpredetermined sampling intervals; drive means for electricallyperforming vertical movement of an optical system for imaging,observation, and measurement of an eye to be inspected; control meansfor controlling the drive means at a speed and in a directionrespectively corresponding to the rotation speed and the rotationdirection of the rotational member that are detected at a currentsampling by the detection means; storage means for storing the rotationspeed and the rotation direction of the rotational member that aredetected by the detection means; and subtraction means for calculating,when the rotation direction at a previous sampling that is stored in thestorage means and the rotation direction at the current sampling are thesame, or when the rotation speed is zero, a rotation speed obtained bysubtracting a predetermined value from the rotation speed at theprevious sampling that is stored in the storage means, in which thecontrol means compares the rotation speed obtained through thesubtraction to the rotation speed at the current sampling, and sets ahigher speed as the rotation speed at the current sampling to be usedfor controlling the drive means.

According to the present invention, the rotation speed of the rotationalpart of the joystick is detected at the predetermined intervals, andwhen the current rotation speed is lower than the previous rotationspeed, the speed obtained by subtracting the predetermined value fromthe previous rotation speed is compared to the current rotation speed.Then, a higher speed is set as the current rotation speed, and the headpart is moved at the speed corresponding to the current rotation speed.Such a configuration can solve the problem inherent in the conventionalcase that, when the rotation speed is high while the rotation amount ofthe rotational part of the joystick is the same, the moving amount ofthe head part conversely decreases. Accordingly, operability can beimproved. Further, even in a case where an inexpensive, small-size motorand a low-output power source are used, the motor can be controlled totrack the rotation amount of the joystick, and thus an inexpensive,small-size apparatus can be provided.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of a joystick.

FIG. 2 is a configuration diagram of a vertical movement mechanism for ahead part.

FIG. 3 is a block diagram of electrical components.

FIG. 4 is a graph showing a relationship between a voltage of a motorand a head moving speed.

FIG. 5 is a graph showing a relationship between a count value of arotary encoder and the voltage of the motor, and between the count valueof the rotary encoder and the head moving speed.

FIG. 6 is comprised of FIGS. 6A and 6B showing flow charts according toa first embodiment of the present invention.

FIG. 7 is an illustration of a relationship between rotation of aconventional joystick and the moving speed of the head part.

FIG. 8 is an illustration of a relationship between rotation of thejoystick and the moving speed of the head part according to the firstembodiment.

FIG. 9 is an illustration of a relationship between rotation of thejoystick and the moving speed of the head part according to a secondembodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

(First Embodiment)

The present invention is described in detail based on exemplaryembodiments illustrated in FIGS. 1 to 6.

FIG. 1 is a schematic configuration diagram of a joystick according to afirst embodiment of the present invention. A ball part 1 has a shaft 2fixed thereto. The shaft 2 has a frame 3 of the joystick fixed thereto.

A plate 4 is fixed to the frame 3, and a rotary encoder 5 and a supportcolumn 9 are fixed to the plate 4. An upper cover 11 of the joystick hasa switch 12 fixed thereto, and the switch 12 is used for startingimaging, measurement, and the like. The upper cover 11 is fixed to thesupport column 9 through the intermediation of a plate 10. A rotationalmember 8 is fitted between the frame 3 and the upper cover 11 so as tofreely rotate. The rotational member 8 has a gear 7 formed inside. Whenthe rotational member 8 rotates, the gear 7 and a gear 6 fixed to ashaft of the rotary encoder 5 rotate in association, and as a result,the shaft of the rotary encoder 5 rotates, thereby detecting a rotationamount of the rotational member 8. The ball 1 is housed in a ballhousing 14 fixed to a stage frame 16 and rolls on a base frame 13 whenthe joystick is inclined, and therefore a stage part is finely movablehorizontally. In a case of rough movement, when a fixed force or more isapplied to the joystick, the ball 1 and the base frame 13 start toslide, and therefore the stage part is greatly movable horizontally. Apin 15 serves as a stop for rotation of the entire joystick, and isinserted into a slit provided to the ball 1. Electric wires extendingfrom the switch 12 and the rotary encoder 5 pass through the supportcolumn 9 and the shaft 2, and further pass through a hole in the ball 1so as to be connected to an electric equipment part (not shown).

FIG. 2 is a schematic configuration diagram of a vertical movementmechanism for a head part. A support column 17 is fixed to the stageframe 16, and a bearing 18 is inserted and fixed inside the supportcolumn 17. A vertical movement shaft 19 is inserted inside the bearing18, and is movable vertically. A head part 22 is fixed to the upperportion of the vertical movement shaft 19. Various kinds of opticalsystem to be used for carrying out imaging, observation, and measurementof an eye to be inspected are built into the head part 22 as anophthalmologic apparatus, but details thereof are not illustratedbecause there is no direct relevance to the present invention. A nut 20threaded into a female screw is fixed to the lower portion of thevertical movement shaft 19. A feed screw 23 is coupled to the inner sideof the nut 20, and a gear 24 is fixed to the lower portion of the feedscrew 23. A motor 26 fixed to the stage frame 16 is a DC motor, and apinion gear 27 is fixed to a rotation shaft thereof. When the motor 26is rotated, the rotation is transmitted to the gear 24 through adeceleration gear 25 coupled to the pinion gear 27. When the gear 24rotates, the feed screw 23 rotates, and the nut 20 coupled to the feedscrew 23 and the vertical movement shaft 19 move accordingly. Therefore,the head part 22 is movable vertically.

A shaft 21 fixed to the support column 17 is used for preventing therotation of the head part 22, and passes through the head part 22.

FIG. 3 is a block diagram of electrical components. The rotary encoder 5is a general two-phase encoder, and transmits pulse signals of phase Aand phase B proportional to the rotation amount to an up/down counter28.

The up/down counter 28 is capable of counting in a positive direction orin a negative direction based on the number of edges and the phase ofthe pulse signals of phase A and phase B. In the present invention, theup/down counter 28 counts in the positive direction when the rotationalmember 8 of the joystick rotates clockwise, and counts in the negativedirection when the rotational member 8 rotates counterclockwise. Hence,the rotation amount and the rotation direction of the rotational member8 of the joystick are detectable. A CPU 29 reads a value counted by theup/down counter 28 every predetermined cycle (for example, every 20msec), stores the value in an internal memory, and sends a clear signalto the up/down counter 28 to clear the counter. The componentsexemplified by the rotary encoder 5, the up/down counter 28, and the CPU29 function as detection means for detecting the rotation speed and therotation direction of the rotational member 8 every predetermined cycle,that is, at predetermined sampling intervals. Further, those componentsmay be defined as a detection unit for repeatedly detecting the rotationamount of the rotational member provided to the joystick. In this case,it is preferred that the pattern of repetition may be set variously asnecessary.

A motor driver 30 for driving the motor 26 controls forward/reverserotation and ON/OFF of the motor based on a rotation direction signaland an ON/OFF signal transmitted from a port of the CPU 29. When theON/OFF signal is set to a Hi level, power is supplied to the motor 26,and when the ON/OFF signal is set to a Low level, the power of the motor26 is turned off.

When the rotation direction signal is set to a Hi level, the motor 26performs forward rotation, and when the rotation direction signal is setto a Low level, the motor performs reverse rotation.

Thus, it may be considered that the CPU 29 constitutes a control unitfor outputting, to the motor driver 30, a control value corresponding tothe detected rotation amount or alternatively the detected rotationdirection and rotation speed.

Further, the rotation speed of the motor 26 is changed by supplying aPWM signal to the ON/OFF signal for the motor driver 30. For example,when a drive voltage of the motor is 12 V, an effective voltage to beapplied to the motor is substantially a voltage expressed by 12×(dutycycle) (V). The duty cycle is expressed by (ON period)/((ON period)+(OFFperiod)), and when the ON period equals the OFF period, the effectivevoltage to be applied to the motor is 6 V. In a case of changing thevoltage to be applied to the motor 26 as described in the embodimentsbelow, such a change is regarded as the change of the effective voltageunder PWM control.

FIG. 4 is a graph showing a relationship between an applied voltage ofthe motor and a moving speed of the head part 22 according to thisembodiment. Due to an influence of friction of a drive system or thelike, when a voltage of a fixed value or larger is applied, the motor 26starts to rotate and thereafter the motor 26 rotates at a rotation speedsubstantially proportional to the applied voltage, thereby moving thehead part 22. In this embodiment, the rotation start voltage is 5 V andthe moving speed of the head part 22 at the maximum applied voltage 12 Vis 14 mm/sec, but needless to say, those numerals vary depending on themotor to be used, the weight of the head part, and the like, and hencediffer among apparatuses.

FIG. 5 is a graph showing a correspondence between a count value of therotary encoder 5 per sampling period and the moving speed of the headpart 22, and between the count value of the rotary encoder 5 and theapplied voltage of the motor 26. The solid line indicates the movingspeed of the head part, and the black spots indicate the applied voltageof the motor 26. The count value of the rotary encoder 5 per unit timeis proportional to the rotation speed of the rotational member 8, andhence the applied voltage is controlled so that the count value has aproportional relationship with the moving speed of the head part 22. Forexample, a voltage of 7.5 V is applied to the motor 26 based on therelationship of FIG. 4 so that when the count value is 5, the movingspeed of the head part 22 is 5 mm/sec.

When the count value is 14, the applied voltage of the motor 26 reachesto 12 V, which is an upper limit voltage of the motor 26, and the movingspeed of the head part at this time is 14 mm/sec. When the count valueis 15 or larger, the upper limit voltage of 12 V is applied to the motor26. When the count value is 15 or larger, the moving speed of the headpart cannot be increased by the motor 26, and thus this count valuecorresponds to an upper limit rotation speed according to the presentinvention.

As described above, the head part 22 serving as the above-mentionedoptical system is vertically driven by the motor 26 serving as drivemeans. Further, the CPU 29 functions as control means for controllingthe moving speed of the head part 22 by the motor 26, and usesinformation on the rotation speed and the rotation direction obtainedfrom the rotational member 8 of the joystick as a command signal forcontrolling the motor 26. Note that, this embodiment exemplifies themotor 26 as the drive means for electrically driving a target object,but the drive means of the present invention is not limited to the motoras long as the drive means is configured to operate electrically andcontrol the operation amount.

Referring to flow charts of FIGS. 6A and 6B, a movement control methodfor the head part 22 according to the rotation of the rotational member8 of the joystick in the ophthalmologic apparatus having theabove-mentioned configuration is described.

First, in Step 1, it is determined whether or not a predeterminedsampling period or interval has elapsed.

After the predetermined sampling period has elapsed, the processingproceeds to Step 2, in which the CPU 29 reads the count value of theup/down counter 28 and stores the count value in the internal memory asa current count value count_now. Note that, the internal memorycorresponds to storage means according to the present invention. The CPU29 reads a positive value when the rotational member 8 of the joystickrotates clockwise, a negative value when the rotational member 8 rotatescounterclockwise, and 0 when the rotational member 8 is being stopped.Because the rotation amount of the rotational member 8 per unit time isdetected, the count value corresponds to the rotation speed of therotational member 8.

In Step 3, the up/down counter 28 is cleared. In Step 4, when a previouscount value count_pre stored in the storage means of the CPU 29 islarger than 0, the processing proceeds to Step 6, while when theprevious count value count_pre is equal to or smaller than 0, theprocessing proceeds to Step 5. In Step 5, when the previous count valuecount_pre is smaller than 0, the processing proceeds to Step 10, whilewhen the previous count value count_pre is 0, the processing proceeds toStep 14.

In Steps 4 and 5, it is determined which of the forward rotation, thereverse rotation, and the stop corresponds to the rotation state of thejoystick in a period from the previous sampling until the currentsampling. Here, the previous sampling and the current sampling may beperformed with a specific time interval set therebetween, andaccordingly, in the present invention, it is preferred that a firsttiming and a second timing be defined as the timing of the previoussampling and the timing of the current sampling, respectively.

In Step 6, when the current count value count_now is equal to or largerthan 0, the processing proceeds to Step 7, while in the other case, theprocessing proceeds to Step 14. In Step 7, a predetermined value issubtracted from the previous count value count_pre, and in Step 8, theprevious count value count_pre after the subtraction is compared to thecurrent count value count_now. When the previous count value count_preis larger, the processing proceeds to Step 9, while in the other case,the processing proceeds to Step 14. Note that, the operation of thissubtraction or subtraction to be carried out subsequently is carried outby a component of the CPU 29 which is defined as subtraction meansaccording to the present invention. Further, the above-mentionedoperation is considered as determination of whether or not a decrease inrotation amount, in which an amount of decrease per unit time in controlvalue obtained by the CPU 29 exceeds a threshold value, has occurred. Inthis case, it is considered that the CPU 29 also serves as adetermination unit for performing the above-mentioned determinationoperation.

In Step 10, when the current count value count_now is equal to orsmaller than 0, the processing proceeds to Step 11, while in the othercase, the processing proceeds to Step 14. In Step 11, a predeterminedvalue is added to the previous count value count_pre, and in Step 12,the previous count value count_pre after the adding is compared to thecurrent count value count_now. When the previous count value count_preis smaller, the processing proceeds to Step 13, while in the other case,the processing proceeds to Step 14.

In Steps 9 and 13, the previous count value count_pre is used as acurrent count value “count”, while in Step 14, the current count valuecount_now is used as the current count value “count”.

In Steps 6 to 14, when the rotation direction of the rotational member 8at the previous sampling and the rotation direction of the rotationalmember 8 at the current sampling are the same, or when the rotationalmember 8 is being stopped, a value obtained by subtracting apredetermined value from the absolute value of the previous count valueis compared to the absolute value of the current count value, and alarger value is set as the count value “count” for driving the currentmotor 26.

In Step 15, when the count value “count” is 0, the processing proceedsto Step 16, in which the CPU 29 sends an OFF signal to the motor driver30 to stop the motor 26. In the other case, the processing proceeds toStep 17, in which the sign of the count value “count” is determined.When the count value “count” is positive, the processing proceeds toStep 18, while when the count value “count” is negative, the processingproceeds to Step 20.

Specifically, when it is determined that the decrease in rotation amountdoes not occur, the CPU 29 sets a sum of the control values to be outputas a first value corresponding to a sum of the detected rotationamounts. On the other hand, when it is determined that the decrease inrotation amount has occurred, the CPU 29 restricts the amount ofdecrease in control value per unit time to a value that avoids exceedingthe threshold value to output, to the motor driver 30, the control valueset so that the sum of the control values becomes larger than the firstvalue.

In this embodiment, the applied voltage of the motor 26 and the movingspeed of the head part 22 have the relationship of FIG. 4, and the countvalue and the applied voltage have the relationship of FIG. 5. The countvalue is proportional to the rotation speed of the rotational member 8,and hence the applied voltage of the motor 26 is expressed bycount×0.5+5 (V). For example, when the count value “count” is 1, theapplied voltage is 5.5 V, while when the count value “count” is 14, theapplied voltage is 12V. The maximum applied voltage is 12 V, and hence,when the count value “count” is 14 or larger, the voltage of 12 V isapplied.

In Steps 18 and 20, the duty cycle of the PWM is set so that theeffective applied voltage of the motor 26 becomes the above-mentionedvoltage. The CPU 29 sends an ON/OFF signal according to the duty cycleto the motor driver 30, and in Steps 19 and 21, the CPU 29 sends signalsindicating the forward rotation and the reverse rotation to the motordriver 30, respectively.

Referring to a graph of FIG. 7, a problem arising when the head part 22is simply driven at a speed proportional to the rotation speed of therotational member 8 is described. The black spots indicate a plot ofcounter values of the rotary encoder obtained according to the speeds ofthe rotational part at the respective samplings, and the solid lineindicates the moving speed of the head part 22. The count value and themoving speed have a proportional relationship. The left side of thegraph indicates a case where the rotational member 8 has undergone sucha rotation operation that the maximum count value becomes the maximummoving speed, and the right side of the graph indicates a case where thespeed is doubled and the rotation amount is the same as compared to therotation operation of the left side. In other words, the right side ofthe graph corresponds to a case where the rotational member 8 isoperated at a rotation speed equal to or higher than the upper limitrotation speed.

In the case of the left side of the graph, the head part 22 is movableat a speed proportional to the count value, while the moving speed ofthe head part 22 on the right side of the graph is peaked out at themaximum moving speed because of the upper limit of the applied voltageof the motor 26, in a range in which the head part 22 is expected to bemoved at a speed indicated by the dotted line. The axis of ordinaterepresents speed, and the axis of abscissa represents time, whichindicates that the area of the solid line portion corresponds to amoving distance. As indicated by the right side of the graph, the movingdistance adversely decreases as the rotational part of the joystick isrotated more quickly.

Referring to a graph of FIG. 8, an operation of this embodiment to beperformed in a case where the rotational member 8 has undergone the samerotation operation as that of FIG. 7 is described. The black spotsindicate counter values of the rotary encoder 5 obtained according tothe speeds of the rotational part at the respective samplings, and thewhite circles indicate count values calculated in the case where thevalue obtained by subtracting the predetermined value (in thisembodiment, 2) from the count value at the previous sampling is largerthan the count value at the current sampling. When the white circle ispresent, the head part is moved at the speed proportional to the whitecircle. As a result, unlike the case of FIG. 7, the area of the solidline portion indicating the moving distance becomes larger as therotational member 8 of the joystick is rotated more quickly as in thecase of the left side of the graph.

In other words, as the joystick is rotated more quickly, the head part22 can be moved more greatly even with the same rotation amount.Further, in a case of fine adjustment, for example, in a case where thecount value is 1 or 2, the motor is stopped instantly when the rotationis stopped, and hence the head part 22 is not moved excessively. In acase where the rotation of the joystick is reversed, the voltage isapplied to the motor 26 so as to achieve the speed and directionaccording to the current count value instead of the previous countvalue, and thus there is no problem with the response.

As described above, as the rotational member 8 of the joystick isrotated more quickly in order to move the head part 22 greatly, themoving amount of the head part 22 becomes larger, and thus operabilityin the case of rough movement is improved. In the case where therotational member 8 is rotated slowly for the fine movement, the headpart 22 is moved at the speed substantially proportional to the rotationspeed, and even when the rotation is reversed, the operation ofreversing the rotation is performed instantly. Thus, there is no problemalso with the operability of the fine movement.

Specifically, with regard to the rotation speed of the rotational member8, which is successively detected by the rotary encoder 5 and theup/down counter 28, when the successively detected rotation speeddecreases and the amount of decrease in rotation speed is larger than apredetermined threshold value (in an extreme case, when the rotation isstopped), instead of the control value corresponding to the detectionvalue, the control value is restricted so that the value does not exceedthe threshold value even though there is a decrease.

If the rotation speed of the rotational member 8 of the joystick isextremely high and the motor 26 is still moving even though therotational part is stopped, the operator may feel inconvenience.Therefore, when the stopped state of the rotational member 8 continuesfor a period corresponding to a predetermined number of samplings ormore and this fact is detected by the detection means, the previouscount value count_pre may be set to 0 to stop the motor 26. Further, inthis embodiment, the value obtained by subtracting the predeterminedvalue (fixed value) from the previous count value count_pre is comparedto the current count value count_now, but alternatively, as in a casewhere a value proportional to the previous count value is used for thesubtraction instead of the fixed value, the predetermined value may bechanged according to the rotation speed detected at the time ofsampling.

(Second Embodiment)

The configuration of this embodiment is the same as that of the firstembodiment, but the control method for the motor 26 in the case wherethe rotational member 8 of the joystick is rotated at high speed ischanged from that of the first embodiment.

Similarly to FIGS. 6A and 6B of the first embodiment, a method ofsolving the problem arising when the head part 22 is simply driven atthe speed proportional to the rotation speed of the rotational member 8is described. A count amount obtained when the speed of verticalmovement of the head reaches to an upper limit speed is represented as“max” (corresponding to the upper limit rotation speed described above;in this embodiment, 14).

FIG. 9 is an illustration of control of this embodiment. The black spotsindicate actual count values and the white circles indicate calculatedcount values. The left side of the graph indicates a case where thecount value does not exceed the value max. When the count valueexceeding the value max is detected as in the case of the right side ofthe graph, a difference between the count value and the value max iscalculated by the subtraction means of the CPU 29, and the difference isstored in the storage means of the CPU 29. The differences obtainedmultiple times during sampling are summed up within the CPU 29 andcalculated as a summed speed, which is stored in the storage means. Thecurrent count value is set to the value max.

Accordingly, the control of the drive means is executed assuming thatthe rotation speed obtained at the current sampling is the upper limitrotation speed. Further, in the case indicated by the right side of thegraph of FIG. 9, the count value exceeding the value max is input threetimes, and hence the summed value that is the summed speed is calculatedas a value expressed by d1+d2+d3 and is stored in the storage means.

When the count value is below the value max, a difference between thevalue max and the current count value is compared to the stored summedvalue, and a smaller value is added to the current count value. Thevalue thus obtained is set as a rotation speed obtained through thecurrent sampling to execute the control of the drive means. Further, thesmaller value obtained through the previous comparison is subtractedfrom the stored summed value by the subtraction means. The sameprocessing is repeated until the summed value becomes 0. Through thisprocessing, as the count value of FIG. 9 for determining the appliedvoltage of the motor 26, the count value indicated by the white circleis used in a case where the white circle is present, and the count valueindicated by the black spot is used in the other case. As a result, themoving speed of the head part 22 proportional to the count value is asindicated by the solid line.

The area of the solid line portion on the left side of the graph equalsthe area of the solid line portion on the right side, and hence themoving speed of the head part 22 corresponds to the moving speedproportional to the rotation amount irrespective of the rotation speedof the rotational member 8 of the joystick. Thus, the operability can beimproved.

Note that, when the stop of the rotational member is detected by thedetection means as many times as the predetermined number of samplingsor more similarly to the first embodiment, the summed speed used at theprevious sampling, that is, the summed speed stored until the previoussampling, may be set to 0 and the above-mentioned processing may beexecuted. Further, when the rotation direction determined based on thesummed speed is different from the rotation direction obtained at thecurrent sampling, the summed speed may be set to 0 to improve theoperability.

According to the above-mentioned embodiment, with regard to the rotationspeed of the rotational member 8, which is successively detected by therotary encoder 5 and the up/down counter 28, when the amount of decreasein rotation speed is larger than the predetermined threshold value, theCPU 29 controls the motor driver 30 so that the amount of decrease inrotation speed of the motor 26 according to the decrease in rotationspeed is smaller than the amount of decrease in rotation speed that hasbeen detected. With this configuration, even when the rotation speed isgreatly increased and then the rotation is not maintained, the amount ofdecrease in rotation of the motor 26 is suppressed. Accordingly, theadjustment amount of the head part 22 can be increased according to theincrease in rotation speed. Further, when the rotational member 8 isrotated so that the amount of decrease in rotation speed becomessufficiently small, the motor 26 can be rotated according to therotation speed of the rotational member 8, and thus fine adjustment ofthe head part 22 is possible.

In the above-mentioned embodiments, the present invention is applied tothe control of rotating the rotational dial of the joystick, but thepresent invention is not limited thereto. The present invention is alsoapplicable to an electrically-driven joystick, in which the joystickitself is rotated.

Note that, the above-mentioned embodiments have described the example inwhich the present invention is applied to the joystick for controllingthe ophthalmologic apparatus, but the control target is not limited tothe ophthalmologic apparatus. For example, the control target may be anapparatus including an arbitrary drive part, or a display control partfor displaying a specific image object on a display part. In thosecases, the drive part is driven according to a control value output froma control part of the joystick, or a display format such as a positionand a size of the displayed image object is changed. Accordingly, therotation amount described in the above-mentioned embodiments is handledas a drive amount. Here, the control part of the joystick is constitutedby a CPU for receiving information on the rotation speed (rotationamount per unit time) and the rotation direction detected by the rotaryencoder and the up/down counter, and outputting the control value. Theprocessing of the present invention can be implemented in such a mannerthat the CPU sequentially loads, on a ROM, programs for performing thesame control as that of the above-mentioned embodiments and executes theprograms thus loaded.

As described above, through the above-mentioned control, the adjustmentamount can be increased according to the rotation speed, and fineadjustment is also possible even without a high-performance motor.

In particular, in the ophthalmologic apparatus, an operation systemincluding the joystick and the rotational member is conventionallywidely used. By applying the present invention to the rotational member,the labor of the operation involved in the adjustment necessitating alarge adjustment amount can be reduced, and fine adjustment can also beperformed with no change of the conventional apparatus and operability.Accordingly, the user can easily adjust the ophthalmologic apparatus,enabling efficient eye diagnosis.

Other Embodiments

Further, the present invention is also implemented by executing thefollowing processing. Specifically, in this processing, software(program) for implementing the functions of the above-mentionedembodiments is supplied to a system or an apparatus via a network orvarious kinds of storage medium, and a computer (or CPU, MPU, etc.) ofthe system or the apparatus reads and executes the program.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-194641, filed Aug. 31, 2010, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A control apparatus for controlling a controltarget, the control apparatus comprising: a joystick; a detection unitfor repeatedly detecting a rotation amount of a rotational memberprovided to the joystick; and a control unit for outputting a controlvalue which corresponds to the rotation amount detected by the detectionunit and which is used for controlling the control target, wherein whenthere has occurred a decrease in the rotation amount, such that anamount of decrease per unit time in the control value exceeds athreshold value, the control unit restricts the amount of decrease perunit time in the control value to a restricted control value that avoidsexceeding the threshold value, and outputs the restricted control value.2. A control apparatus according to claim 1, further comprising adetermination unit for determining whether or not the decrease in therotation amount, in which the amount of decrease per unit time in thecontrol value exceeds the threshold value, has occurred, wherein when itis determined that the decrease in the rotation amount does not occur,the control unit outputs the control value such that a sum of controlvalues to be output is a first value which corresponds to a sum of thedetected rotation amounts, and wherein when it is determined that thedecrease in the rotation amount has occurred, the control unit restrictsthe amount of decrease per unit time in the control value to arestricted control value that avoids exceeding the threshold value, andoutputs the restricted control value so that a sum of control values tobe output becomes larger than the first value.
 3. A joystick apparatusfor controlling a control target, the joystick apparatus comprising: anoperation stick; a detection unit for repeatedly detecting a rotationdirection and a rotation speed of a rotational member provided to theoperation stick; and a control unit for outputting a control value whichcorresponds to the rotation direction and the rotation speed that arerepeatedly detected, and which is used for controlling the controltarget, wherein when an amount of decrease in a rotation speed detectedat a first timing with respect to a rotation speed detected at a secondtiming preceding the first timing is larger than a threshold value, thecontrol unit restricts a decrease per unit time in the control value andoutputs a restricted control value.
 4. A joystick apparatus according toclaim 3, wherein a period required until the control value reaches to acontrol value which corresponds to the rotation speed detected at thefirst timing from a control value corresponding to the rotation speeddetected at the second timing is longer in a case where the amount ofdecrease in the rotation speed is larger than the threshold value thanin a case where the amount of decrease in the rotation speed is smallerthan the threshold value.
 5. A joystick apparatus according to claim 3,wherein the control value comprises a drive amount of a drive part fordriving the control target.
 6. An ophthalmologic apparatus, comprising:the apparatus according to claim 1; and an optical unit that is thecontrol target.
 7. A control method for an apparatus including ajoystick for controlling a control target, the control methodcomprising: repeatedly detecting a rotation amount of a rotationalmember provided to the joystick; outputting a control value whichcorresponds to the rotation amount detected by the detecting and whichis used for controlling the control target; determining whether or notthere has occurred a decrease in the rotation amount such that an amountof decrease per unit time in the control value exceeds a thresholdvalue; outputting, when it is determined that the decrease in therotation amount does not occur, the control value so that a sum ofcontrol values to be output becomes a first value which corresponds to asum of the detected rotation amounts; and restricting, when it isdetermined that the decrease in the rotation amount has occurred, theamount of decrease per unit time in the control value to a restrictedcontrol value that avoids exceeding the threshold value, and outputtingthe restricted control value so that a sum of control values to beoutput becomes larger than the first value.
 8. An ophthalmologicapparatus, comprising: detection means for detecting a rotation speedand a rotation direction of a rotational member provided to a joystickat predetermined sampling intervals; drive means for electricallyperforming vertical movement of an optical system for imaging,observation, and measurement of an eye to be inspected; control meansfor controlling the drive means at a speed and in a directionrespectively corresponding to the rotation speed and the rotationdirection of the rotational member that are detected at a currentsampling by the detection means; storage means for storing the rotationspeed and the rotation direction of the rotational member that aredetected by the detection means; and subtraction means for calculating,when the rotation direction at a previous sampling that is stored in thestorage means and the rotation direction at the current sampling are thesame, or when the rotation speed is zero, a rotation speed obtained bysubtracting a predetermined value from the rotation speed at theprevious sampling that is stored in the storage means, wherein thecontrol means compares the rotation speed obtained through thesubtraction to the rotation speed at the current sampling, and sets ahigher speed as the rotation speed at the current sampling to be usedfor controlling the drive means.
 9. An ophthalmologic apparatus,comprising: detection means for detecting a rotation speed and arotation direction of a rotational member provided to a joystick atpredetermined sampling intervals; drive means for electricallyperforming vertical movement of an optical system for imaging,observation, and measurement of an eye to be inspected; control meansfor controlling the drive means at a speed and in a directionrespectively corresponding to the rotation speed and the rotationdirection of the rotational member that are detected at a currentsampling by the detection means; storage means for storing the rotationspeed and the rotation direction of the rotational member that aredetected by the detection means, and further storing an upper limitrotation speed corresponding to an upper limit of a rotation speed ofthe drive means, and a difference between the upper limit rotation speedand the rotation speed in a case where the detected rotation speed ofthe rotational member exceeds the upper limit rotation speed; andsubtraction means for subtracting the upper limit rotation speed fromthe rotation speed to calculate the difference, wherein when a currentrotation speed of the rotational member exceeds the upper limit rotationspeed, the control means sums up the differences stored in the storagemeans to calculate a summed speed, which is stored in the storage means,and sets the upper limit rotation speed as the current rotation speed tobe used for controlling the drive means, and wherein when the rotationspeed is lower than the upper limit rotation speed, the control meanscompares the summed speed to a current difference obtained bysubtracting the current rotation speed from the upper limit rotationspeed stored in the storage means, subtracts a lower rotation speed fromthe summed speed to obtain a new summed speed, which is stored in thestorage means, and sets a speed obtained by adding the lower rotationspeed to the current rotation speed, as the current rotation speed to beused for controlling the drive means.
 10. An ophthalmologic apparatusaccording to claim 8, wherein when a stop of the rotational memberprovided to the joystick is detected by the detection means as manytimes as a predetermined number of samplings or more, the control meanssets the rotation speed of the rotational member at the previoussampling to zero.
 11. An ophthalmologic apparatus according to claim 8,wherein the control means changes the predetermined value subtractedfrom the rotation speed at the previous sampling according to therotation speed at the previous sampling.
 12. An ophthalmologic apparatusaccording to claim 9, wherein when a stop of the rotational memberprovided to the joystick is detected by the detection means as manytimes as a predetermined number of samplings or more, the control meanssets the summed speed used at a previous sampling to zero.
 13. Anophthalmologic apparatus according to claim 9, wherein when the rotationdirection determined based on the summed speed is different from therotation direction at the current sampling, the control means sets thesummed speed to zero.